SE-11
a) Draw P – V and T – S diagram for a single stage reciprocating air compressor, without clearance. Derive the expression for the work done
when compression is a) Isothermal b) Isentropic.
b) Determine the size of the cylinder for a double acting air compressor of 40 kW indicated power, in which air is drawn in at 1 bar and 15 °C
and compressed according to the law PV1.2 = constant, to 6 bar. The compressor runs at 100 r.p.m. with average piston speed of 152.5
m/min. Neglect clearance.
a) Show that intermediate pressure in a two stage reciprocating air compressor is a geometric mean of suction and discharge pressures.
b) A four stage compressor works between limits of 1 bar and 115 bar. The index of compression in each stage is 1.28. The temperature at the
start of compression in each stage is 35 °C and intermediate pressure are so chosen that the work is divided equally amongst stages.
Neglecting clearance, calculate
i) Pressures P2, P3 and P4
ii) Isothermal efficiency
iii) Delivery temperature in each stage.
a) Explain with suitable sketches the working of two stroke engine.
b) Explain how actual cycle deviates from theoretical cycles.
c) What are the assumptions made in the analysis of fuel air cycle?
a) Draw a neat sketch of a four stroke S.I. Engine, label the parts and explain their functions.
b) A Diesel engine has a compression ratio of 20 and cat. off takes place at 5% of stroke. Find air standard efficiency.
Unit –
a) What are the basic elements of C.I. Engine fuel injection system? Explain their functions with schematic diagram.
b) What are the functions of carburetor? Explain any one type of carburetor with the help of neat sketch.
a) What is petrol injection? What are its advantages over carburetor engine?
b) List the types of fuel injectors and explain with a neat sketch working of any one type of fuel injector.
c) What are the air fuel ratio requirements of petrol engine under different loading conditions ?
Unit –
a) What are the various components to be lubricated in I.C. Engine ? and explain how it is accomplished.
b) What are the harmful effects of overheating of I.C. Engines ?
c) Why is governing of I.C. Engines required ? Enlist the methods used for governing of I.C. engines.
a) Explain pressure lubrication system.
b) Why is spark advance required ? Explain any one spark advance mechanism with sketch.
c) Differentiate between evaporative cooling and forced circulation cooling.
Unit –
a) What are the various methods of measuring indicated power? Briefly compare their relative accuracy. Explain any one method in detail.
b) A four stroke four cylinder S.I. Engine has a compression ratio of 8 and bore of 100 mm with stroke equal to bore. The volumetric efficiency
of each cylinder is equal to 75%. The engine operates at a speed of 4800 rpm with an air fuel ratio 15. Given that the calorific value of fuel 42
MJ/kg. density of atmospheric air 1.12 kg/m3, mean effective pressure in the cylinder is 10 bar and mechanical efficiency of engine 80%,
determine indicated thermal efficiency of the brake power. 10
a) Explain the factors that limits the extent of supercharging in S.I. and C.I. engine. 8
b) In a trial on a single cylinder oil engine working on duel cycle, the following observations were made
Compression ratio = 15
Oil consumption = 10.2 kg/h
Calorific value of fuel = 43890 kJ/kg
Air consumption = 3.8 kg/min
Speed = 1900 rpm
Torque on brake drum = 186 N-m
Quantity of cooling water used = 15.5 kg/min
Temperature rise = 36°C
Exhaust gas temperature = 410°C
Room temperature = 20°C
Specific heat of exhaust gas = 1.17 kJ/kg K
Calculate brake power, brake specific fuel consumption, brake thermal
efficiency and heat balance sheet per minute basis. 10
Unit –
a) Draw the schematic sketch and mention merits and demerits of the following type of combustion chambers in I.C. Engines.
i) Hemispherical combustion chamber in S.I. engine
ii) M. Combustion chamber in C.I. Engine. 10
b) What is diesel knock ? How dose knocking in a diesel engine differ from detonation in petrol engine? 6
a) What are the requirements of good combustion chambers used in S.I. Engine and C.I. Engines? 5
b) Discuss the effect of the following engine variables on flame propagation
i) Air fuel ratio
ii) Compression ratio
iii) Load
iv) Speed. 6
c) What is meant by ignition delay in diesel combustion ? Discuss the variables affecting delay period. 5
Unit –
a) Discuss in brief the various design and operating parameters responsible for formation of
i) Carbon monoxide
ii) Hydrocarbons
iii) Oxides of nitrogen in petrol and diesel engine. 6
b) Write short note on : 10
i) Hybrid vehicle
ii) Engine selection (for any application).
a) What is smoke ? What are the bad effects of smoke on human health and how smoke in diesel engine can be controlled ? 6
b) Discuss briefly the following with regard to S.I. Engines :
i) Crank case emission
ii) Evaporative emission
iii) Exhaust emission. 10
SE Oct 11
(a) Explain Vane compressor with sketch. [6]
(b) Prove that condition for minimum work required for a two stage reciprocating air compressor is :
P2 = P1 . P3 where P1-intake and P3-delivery pressure. [8]
(c) A single stage, single acting compressor delivers air from 1 bar to 7 bar. Assuming compression follow the law PV1.35 = constant and
clearance 5% of the swept volume, find volumetric efficiency of a compressor.
(a) Draw and explain actual PV diagram for single stage reciprocating
air compressor. [6]
(b) Define :
Isothermal efficiency
Volumetric efficiency
Free air delivered in case of compressor. [6]
(c) Free air to be compressed from 1 bar to 15 bar pressure. Two alternatives are available i.e. single stage and multistage compression.
Assuming polytropic index 1.3, justify which alternative should be used by calculating work. Assume perfect intercooling. [6]
(a) Derive an expression for thermal efficiency of a Diesel cycle with usual notations. Hence show that the efficiency of the Diesel cycle is lower
than that of Otto cycle for the same compression ratio. Comment why the higher efficiency of Otto cycle compared to Diesel cycle have no
practical importance. [9]
(b) The mean effective pressure of an ideal Diesel cycle is 8 bar. If the initial pressure is 1.03 bar and the compression ratio is 12, determine
the cut-off ratio and the air-standard efficiency. Take Y air as 1.4. [9]
(a) How do the specific heats vary with temperature? What is the physical explanation for this variation?
(b) Compare Air-standard cycle, fuel-air cycle and actual cycle of a gasoline engine. [5]
(c) Fuel supplied to an SI engine has a calorific value 42000 kJ/kg. The pressure in the cylinder at 30% and 70% of the compression stroke are
1.3 bar and 2.6 bar respectively. Assuming that the compression follows the law pV1.3 = constant, find the compression ratio. If the relative
efficiency of the engine compared with the air-standard efficiency is 50%, calculate the fuel consumption in kg/kW hr. [8]
a) Describe with suitable sketches the following systems of a modern carburetor:
(i) Main metering system
(ii) Economizer system and
(iii) Choke.
[9]
(b) A four-cylinder, four stroke square engine running at 40 rev/sec. has a carburettor venturi with 3 cm throat. Assuming the bore to be 10 cm,
volumetric efficiency 75%, the density of air to be 1.15 kg/m3 and coefficient of air flow to be 0.75. Calculate the suction at the throat. [7]
(a) What action can be taken with regard to the following variables, in order to reduce the possibility of detonation in an S.I. engine ? Justify
your answers by reasons :
(i) Mass of charge induced
(ii) Spark timing
(iii) Distance of flame travel and
(iv) Engine speed. [8]
(b) Explain the phenomenon of pre-ignition. How pre-ignition leads to detonation and vice-versa ? Explain how pre-ignition can be detected ?
[8]
(a) Explain the stages of combustion in a CI engine. [6]
(b) What is the importance of delay period ? Should the delay period be zero ? [4]
(c) Explain the following : [6]
(i) Pre-combustion chamber
(ii) M combustion chamber.
(a) How do the injection timing and the fuel quality affect the engine knock ? [4]
(b) Discuss the requirements of an ideal injection. [4]
(c) Describe the principle of a helix bypass pump and draw sketches for different types of plunger helix in use. [8]
(a) Explain any one type of Electronic Ignition System. [8]
(b) What do you mean by drive train mechanism? Explain with sketches. [8]
(a) What is governing of IC engines ? Explain Hit and Miss governing. [8]
(b) What do you mean by intake and exhaust system ? Explain with sketches various parts of intake and exhaust systems in brief. [8]
(a) What are the various methods for measuring friction power ? Describe the ‘Motoring method’ of measurement of friction power. [8]
(b) A 4-cylinder petrol engine with 80 mm bore and 110 mm stroke length working on 4-stroke principle develops torque 140 N-m at 4500 rpm.
The clearance volume per cylinder is 0.065 litres.
Fuel consumption is 16 kg/hr. Take C.V. of fuel as 42500 kJ/kg and was 1.4 for air.
Calculate :
(i) B.P.
(ii) bmep
(iii) Brake thermal efficiency and
(iv) Relative efficiency. [10]
(a) Explain the limitations of Supercharging. [4]
(b) Describe with a sketch the principle of a hydraulic dynamometer. [8]
(c) A single cylinder engine running at 2000 rpm develops a torque of 10 N-m. The indicated power of the engine is 2.3 kW. Find the loss due
to friction power as the percentage of brake power. [6]
(a) Enlist the specifications of an automotive engine. [8]
(b) Explain exhaust gas recirculation system to control oxides of nitrogen. [8]
(a) Explain Hybrid Electric-vehicle (HEVs). [8]
(b) Explain :
(i) Compressed Natural Gas (CNG)
(ii) Liquefied Petroleum Gas (LPG).
S -12
(a) Discuss the different methods of capacity control used for reciprocating compressor. [6]
(b) Define clearance ratio in air compressor. What is its effect on work and volumetric efficiency ? [4]
(c) A single stage single acting reciprocating air compressor has air entering at 1 bar, 20ºC and compression occurs following polytropic
process with index 1.2 up to delivery pressure of 12 bar. The compressor runs at the speed of 240 rpm and has L/D ratio of 1.8. The
compressor has mechanical efficiency of 0.88. Determine the isothermal efficiency and cylinder dimensions. Also find out the rating of drive
required to run the compressor which admits 1 m3 of air per minute. [8]
(a) Draw P-V and T-S diagram for a single stage reciprocating air compressor without clearance. Derive the expression for work done when
compression is :
(i) Isothermal and
(ii) Isentropic. [6]
(b) Explain the working of Root blower with a neat sketch. [4]
(c) A reciprocating air compressor has four stage compression with 2 m3/min of air being delivered at 150 bar when initial pressure and
temperature are 1 bar 27ºC. Compression occur polytropically
Following polytrophic index of 1.25 in four stages with perfect intercooling between stages. For the optimum intercooling conditions determine
the intermediate pressures and the work required for driving compressor.
a)Draw self explanatory p-V diagrams of theoretical and actual dual cycles. [4]
(b) “Actual thermal efficiency of an engine is much less than
that of theoretical/ideal efficiency.” Justify by giving any 4 reasons. [4]
(a) Derive the expression for efficiency of standard Otto cycle. [6]
(a) What are the drawbacks of carburettor system in S.I. engines ? Explain MPFI system for gasoline engine with the help of neat diagram. [8]
(a) Higher compression ratio (CR) increases the thermal efficiency of engines, then why CR of diesel engine range (say 16 to 21) are not
adopted in petrol engines ? Explain the phenomenon with the help of diagram. [8]
(b) Write short notes on : [8]
(i) Pre-ignition
(ii) Auto-ignition
(iii) HUCR
(iv) Delay period and ignition lag.
(a) With the help of neat p-θ diagram, explain combustion stages in C.I. engines. [8]
(b) What are the objectives of combustion chamber design for diesel engines ? Differentiate between DI and IDI combustion chambers.
Explain any one swirl combustion chamber with a diagram. [10]
(a) “Gasoline engines are generally not supercharged but C.I. engines are supercharged.” Justify. Explain general turbo charging system of an
engine with the help of neat diagram. [8]
(b) Draw the labeled layout of fuel system in C.I. engine. Explain the working of Bosch Fuel Pump (Jerk type individual pump) with the help of
diagram. [10]
Unit
(a) List down various parts of battery ignition system and explain it briefly with neat sketch. [8]
(b) Compare between air cooling system and water cooling system. [4]
(c) Explain briefly overhead valve mechanism. [4]
(a) Explain with neat sketch dry sump lubrication system. [8]
(b) Write a note on electric arrangement of engine starting system. [4]
(c) Write advantages of electronic ignition system over conventional ignition system. [4]
Unit
(a) In a test of an oil engine under full load condition, the following results were obtained : [12]
Indicated power = 33 kW
Brake power = 27 kW
Fuel used = 8 kg/h
Rate of flow of water through gas calorimeter = 12 kg/min
Cooling water flow rate = 7 kg/min
Calorific value of fuel = 43 MJ/kg
Inlet temperature of cooling water = 15°C
Outlet temperature of cooling water = 75°C
Inlet temperature of water to exhaust gas calorimeter = 15°C
Outlet temperature of water to exhaust gas calorimeter = 55°C
Final temperature of the exhaust gases = 80°C after calorimeter
Room temperature = 17°C
Air-fuel ratio on mass basis = 20
Mean specific heat of exhaust gas = 1 kJ/kgK
Specific heat of water = 4.18 kJ/kgK.
Draw up a heat balance sheet on kJ/min basis and estimate the brake thermal and mechanical efficiencies.
(b) Explain Willan’s line method and give out its limitations. [4]
(a) An eight cylinder, four stroke engine of 0.09 m bore and 0.08 stroke with a compression ratio of 7 is tested at 4500 r.p.m. on a
dynamometer which has 0.54 m arm. During 10 min test the dynamometer scale beam reading was 42 kg and the engine consumed 4.4 kg of
gasoline having calorific value of
44000 kJ/kg. Air 27°C and 1 bar was supplied to the carburettor at the rate of 6 kg/min. Take R = 287J/kgK.
Find :
(i) the brake power delivered
(ii) the brake mean effective pressure
(iii) the brake specific fuel consumption
(iv) the brake thermal efficiency
(v) the volumetric efficiency
(vi) the air-fuel ratio.
(b) Explain air box method for air consumption measurement. [4]
S 2013
Define:
1) Isothermal efficiency
2) Volumetric efficiency
3) F.A.D
(b) Explain Vane compressor with a neat sketch
(c) For a single stage single acting reciprocating air compressor, actual volume of air taken in is 10m3/min. Initial intake pressure is 1.013 bar
and initial temp is 27°C. Final pressure is 900Kpa, clearance is 6% of stroke.
Compressor runs at 400 rpm.
Assume: L/D = 1.25 and index of compression = 1.34
Determine : 1) volumetric efficiency
2) Cylinder dimensions
3) Indicated power [06]
(a) Explain the methods of improving isothermal efficiency of air compressor [06]
(b) A 2 stage single acting compressor takes in air at 1 bar and 300k. Air is discharged at 10bar. The intermediate pressure is ideal and
intercooling is perfect. The law of compression is PV1.3=C
The rate of discharge is 0.1 kg/sec. Find
1) Power required to drive the compressor
2) Saving in work compared to single stage
3) Isothermal efficiency for single and multistage
4) Heat rejected in intercooler
Take Cp= 1kj/kg k and R= 0.287 kj/kg k [10]
A) Compare Otto, and Dual cycle for: (8)
i. Constant maximum pressure and same heat input
ii. Same compression ratio and same heat input
iii. Same max pressure and same output
B) A S.I. engine working on Otto cycle takes the air in at 0.97 bar (10) and 40˚C. The compression ratio of the cycle is 7. The heat supplied
during the cycle is 1.2 MJ/kg of working fluid. Find:
i. Air standard efficiency of the cycle
ii. Maximum temperature attained in the cycle
iii. Maximum pressure attained in the cycle
iv. Work done per kg of working fluid
v. Mean effective pressure
Take ϒ=1.4, Cv=720J/kg-k
A) Derive an expression for thermal efficiency of a diesel cycle with usual notation.
B) Explain pumping and friction losses and their effects on the power Output of the engine.
C) State the assumption made for air standard cycle. (5)
A) Explain with neat sketch the following systems of a carburetor (7)
i. Idling system
ii. Chock
B) The diameter for a venture of a simple carburetor is 2cm and its (9)
Cda=0.85. The fuel nozzle diameter is 1.25 mm and Cdf=0.66.
The lip of the fuel nozzle is 5 mm. Find:
i. A:F ratio for pressure drop of 0.07 bar when nozzle lip is neglected.
ii. A:F ratio when the nozzle lip is considered.
iii. The minimum velocity of air required to start the fuel flow when lip Provided.
Take density of air = 1.2 kg/m3 and density of fluid=750 kg/m3.
A) Explain the basic requirements of a good combustion chamber of S.I. engine and draw a neat sketch of T-head combustion chamber.
B) Explain the phenomenon of pre-ignition. How pre-ignition leads to detonation and vice-versa? Explain how pre-ignition can be detected?
A) How air-less injection systems are classified? Explain the working of distributer system with the help of neat sketch. Discuss their relative
merits and demerits.
B) What are the functions of a nozzle? Explain various types of nozzles With neat sketches.
A) Explain the stage of combustion in CI engine. (8)
B) What is meant by ignition delay? Explain the effect of following factors on the ignition delay with suitable reason.
i. Compression Ratio
ii. Engine size
iii. Engine speed
A) What are the basic requirements of an ideal ignition system? (4)
B) What are the desirable properties of good lubricating oil? (4)
C) What are the main functions of lubricating system? Explain dry Sump lubricating system.
A) Define the functions of radiators. Discuss different type of matrices used with these radiators with neat sketch.
B) Explain the working of spring loaded mechanical governor with the help of neat sketch used for Diesel engine.
A) The following observations are made during a trial on an oil engine (12)
-Motor power to start the engine =10kW
-R.P.M.=1750
-Brake Torque = 327.5Nm
-Fuel used = 15 kg/hr
-C.V. of fuel used = 42MJ/kg
-Air supplied = 4.75 kg/min
-Quantity of cooling water = 16 kg/min
-Outlet temperature of cooling water = 65.8˚C
-Room temperature = 20.8˚C
-Exhaust gas temperature = 400˚C
-Take Cpw = 4.2kj/kg. K and Cpg = 1.25kj/kg.K
Determine :
i. B.P.
ii. Mechanical efficiency
iii. BSFC
iv. Draw a neat balance sheet on k W basis and percentage basis.
B) Write a short note on: (6)
i. Heat balance sheet.
ii. Various factors affecting volumetric efficiency.
A) A six cylinder gasoline engine operators on the four stroke cycle. The bore of each cylinder is 80 mm and stroke 100 mm. the clearance
Volume per cylinder is 70CC. At a speed of 4000 r.p.m., the fuel Consumption is 30 kg/hr. and the torque developed is 150 N.m
Calculate:
i. The brake power
ii. The brake mean effective pressure
iii. The brake mean thermal efficiency
Assume the C.V. of fuel as 43,000 kJ/kg. Also estimate relative efficiency
When engine works on constant volume cycle with = 1.4 for air.
B) What is the dynamometer? Name the various types of dynamometer. Explain the Eddy current dynamometer with the help of a neat sketch.
A) Enlist the specification of an automobile engine. (6)
B) What is air pollution? Explain the contributors to air pollution and (6) their harmful effects on humans beings.
C) Mention the modifications required if hydrogen is used in SI engine As a substitute fuel.
Write short notes on: (16)
i. Hybrid electric vehicle
ii. Emission control methods for IC engines.
iii. Exhaust gas recirculation.
iv. Euro norms